code: def get_notebook_title(nb_json, default=None):
      """Determine a suitable title for the notebook.
  
      This will return the text of the first header cell.
      If that does not exist, it will return the default.
      """
      cells = nb_json["cells"]
      for cell in cells:
          if cell["cell_type"] == "heading":
              return cell["source"]
      return default
  
file_path: mpld3/doc/sphinxext/notebook_converter.py
imports: import sys
  import os
  import glob
  import shutil
  import jinja2
  import nbformat
  from nbconvert.exporters import HTMLExporter
label_desc: Use image node_id 1 for calling a global function with example usage: get_notebook_title(nb_json, default) and returns: default, cell